Adjustable compensated standard



Nov. l1, 1947.

H. T. WILHELM 2,430,488 ADJUSTABLE coMPENsATED STANDARD Filed sept. '2,1943 3 Sheets-Sheet l POWER SOURCE @y HT. w/HsLM ma@ Nov. 11, 1947. JH.T.wn HE1 M 2.430,488

ADJUSTABLE COMPENSA-TED STANDARD Filed Sept. 2,-1943 3 Sheets-Sheet 2www W0 ATTORNEY Nov. ll, 1947. H. T. WILHELM 2,430,483

ADJSTABLE COMPENSATED STANDARD FledlSepL 2, 1943y 3 Sheets-Sheer?l 3 l/NVE/VTOR H 7 W/LHELM .Bywmw ya@ ATTORNEY Patented Nov. 11, 1947ADJUSTABLE COMPENSATED STANDARD Henry T. Wilhelm, Long Island City, N.Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N.Y., a corporation of New York Application September 2, 1943, Serial No.500,936

13 Claims. 1

This invention relates to alternating current bridge circuits and moreparticularly to compensated admittance and impedance standards lindingspecial applications in alternating current bridges.

One of the difculties which constantly face users of alternating currentbridges is that while adjusting one particular admittance or impedancecomponent, other components are also varied by reason of impuritiesinherent in the bridge standard, thereby complicating the balancingadjustment and greatly increasing the time required to make themeasurement. A very desirable advantage would be realized by maintainingconstant all components not being adjusted.

It is therefore the object of this invention to provide an alternatingcurrent bridge standard for an alternating current bridge which, whileany one component thereof is being adjusted, maintains all othersconstant.

The foregoing object is achieved by this invention by providing incombination an adjustable compensated alternating current bridgestandard comprising a pair of terminals for said standard, a multipleposition switching means, a plurality of standard circuit elementshaving undesired circuit components inherent therein, one compensatingelement for each standard element having components of the same kindsand magnitudes as the undesired inherent circuit components of itsstandard element, circuits connecting the standard elements, thecompensating elements and the switching means to the pair of terminals,said circuits and switching means being adapted to selectively connectthe standard elements in a plurality of predetermined combinationsbetween said pair of terminals and to automatically substitute betweensaid terminals the compensating element for each standard element not soconnected.

The invention may be better understood by referring to the accompanyingdrawings, in which:

Fig. 1 discloses a Maxwell type bridge il1ustrative of one of the typesof bridges which may utilize this invention;

Fig. 2 discloses a schematic of the essential elements of a practicalstandard admittance which may be used in the Maxwell bridge of Fig. 1;

Fig. 3 discloses how the standard admittance schematically disclosed inFig. 2 may be constructed in accordance with this invention;

Fig. 4 discloses one form of switching mechanism which may be employedto practice this invention;

Fig. 5 discloses a decade type conductance standard employingcommercially available radial type switches;

Fig. 6 discloses a capacitance decade employing commercially availableradial type switches;

Figs. '7 and 8 disclose conductance and capacitance decade unitsrespectively, each employing a drum type switch; and

Fig, 9 discloses the invention applied to an inductance standard.

Fig. 1 shows how the invention may be embodied in a Well-known Maxwelltype inductance measuring bridge. A detail description of this bridgeand its properties may be found in any standard work on electricalmeasurements, reference, however, being made to Bell Laboratories Recordfor November 1940, page 92, for a brief description of the principles ofthis bridge. In the simple form shown in Fig. 1 the bridge comprisesfour arms, two opposite arms comprising resistors Rl and R2, while oneof the other two arms comprises the standard admittance Ys and thefourth arm the unknown impedance Zx in series with a balancing impedanceZb. A suitable power source I is connected to the B and D corners of thebridge and a suitable detector to the A and C corners of the bridge.Except for the shielding shown on the standard admittance and thebalancing impedance, all shielding is deleted for the sake of clarity.Shielding would, of course, be used and may be applied in accordancewith established principles. An important advantage of the Maxwellbridge is that an unknown inductance Lx may be measured by using acapacitance standard which is more easily constructed with low lossesand with accuracy than is a standard inductance. The unknown inductiveimpedance ZX may contain an unknown resi-stive component RX, the compleximpedance being expressed in the familiar form Rx-l-iwLx. The Maxwellbridge permits the standard to be expressed most conveniently in theform of a complex admittance ys so that the balance equation is:

In a practical bridge structure the product R1R2 is made equal tosome'power of ten so that the resistance component Rx is measured by thestandard conductance GS and the inductance Lx by the capacitance cs.

A schematic of the essential elements of a practical standard admittancefor the Maxwell bridge is shown in Fig. 2. It is obvious that if thebridge is to balance for an unknown inductive impedance having anegligibly small resistive component Rx, the admittance standard musthave a conductance component Gs which is also very small. For practicalreasons the construction of such small conductances is not feasible andis avoided by including in the admittance standard a residualconductance GR, usually in the form of a slide wire in series with aresistor which is balanced by the resistive component Rb of thebalancing impedance Zt. Also it is impossible to construct any practicalalternating current standard admittance or impedance without incurringsome spurious unwanted components usually in the form of capacitivesusceptances for admittance standards and resistances for impedancestandards. In this invention these components are utilized as a part ofthe residual components of the bridge and are automatically keptconstant so as not to continuously upset the balancing adjustment forone component while adjusting another. In this way the undesiredcomponents are at all times completely compensated.

In Fig. 2 the residual conductance GR and the residual capacitance Caare each kept constant. In the practical decade standard the residualconductance comprises a iixed conductance element connected as shownschematically in Fig. 2. However, the residual capacitance CR comprisesnot only physical capacitors but also the capacitance of the wiringandswitch elements of the decade standard. VThe total admittance may thenbe expressed as YsIGs-i-LUCS: (gs-l-jwcs) (GR--Y'wcl) In the aboveexpression the quantity (GR-HwCR) is the residual admittance constantfor any given test frequency, while the quantity (gS-l-jwcs) is thevariable admittance equal to ys in Equation 1. It will be obvious tothose skilled in the art that the constant quantity (GR-i-y'wCR) is notobjectionable as it may be balanced by inserting in the C-D arm abalancing impedance Zb. It is also clear that if this quantity is to bekept constant as is contemplated by this invention, the initial balanceof the bridge is in no way upset and any variations which take place inthe admittance standard are incurred by reason of the adjustment or thevarious variable components of the standard unit. The variablecomponents, therefore, are a direct measure of the unknown impedance Zxwhich is connected to the terminals Xi and X2 of the bridge of Fig. 1.

Referring now to Fig. 3 which discloses the schematic of a practicalembodiment of this invention, illustrating how an admittance unit of thegeneral form shown in Fig. 2 may be constructed, the two terminals ofthis standard admittance carry the reference characters A, B whichcorrespond to the A, B terminals of the bridge in Fig. l. Between 'thesetwo terminals is shown permanently connected the constant conductance GRand capacitance Ca. As previously stated, the constant conductance GR ina practical'st'ructure usually comprises a physical conductanceconnected between these two terminals as well as the lumped leakageconductance. The constant capacitance Ca represents not only a physicalcapacitance whichmay be connected between the two terminals but also thetotal stray capacitance existing between the wiring and the switchterminals of both the conductance and capacitance standard componentelements shown in Fig, 3. At this point it may be mentioned that in apractical structure it is preferable that the balancing impedance Zt bemade without adjustment in which event the constant capacitance Ca ofthe admittance standard shown in Fig. 3 may also include a variablecondenser to aid in securing the initial balance with terminals Xi andX2 short-circuited. In any event after initial balance is secured thevalue of the capacitance CR remains invariable.

t is a well-known tact that it is very difficult to construct standardcircuit elements Without including impurities which are herein termedundesirable components. Although various types of improved constructionmay be employed to reduce their magnitudes, no construction has beenfound to eliminate them entirely. In accordance with this invention theyneed not be eliminated but in so far as adjusting the standard elementsis concerned their presence in no way disturbs the initial balance oithe bridge. For the conductance decade gs, shown in Fig. 3, this isaccomplished by compensating the conductance elements by connecting inseries therewith compensating capacitors such as C1, C2, C3 and C4, thecapacitances of which are exactly equal to the spurious capacitances oitheir associated conductance elements. It is here assumed that all otherspurious components are negligible but should they be appreciable, theymay be compensated in exactly the same way. The function oi theswitching arrangement is then to either short-circuit the compensatingcapacitance or short-circuit the standard conductance element whichinherently includes the stray capacitance to be compensated. Forexample, in Fig. 3 the ten-micromho conductance unit must be understoodto have inherent therein a capacitance component equal to Ci. Thereforea compensating condenser Ci is connected in series with this conductanceunit. A two-position switch with a blade-3 is connected to terminal 6joining this compensating capacitor C1 and the ten-micromho conductanceunit. The switch is caused to engage either switch point 4 or switchpoint 5. When it is in engagement with point 5, as shown in Fig. 3, theten-micromho standard element is short-circuited thereby eliminatingthis conductance standard element from the circuit between the standardterminals A, B. It Will be noted that in this position compensatingcapacitor C1 is vinserted between these two standard terminals A and B.The eiect is to remove the ten-micromho standard element from thecircuit while leaving intact between the two standard terminals thecapacitance Ci which corresponds to the undesired inherent capacitancecomponent of the standard ten-micromho element. When this switch blade 3is switched to point 4, the compensating capacitance C1 is switched outof the circuit and the ten-micromho element is connected to theterminals A and B along with its inherent capacitance component equal tothe capacitance of capacitor C1. Each of the two conductance elementsalso has a similar capacitor connected in series therewith which in eachcase is exactly equal in capacitance to the stray capacitance inherentin its associated conductance element. It will be understood that byswitching switch blades 3 of Vthese conductance units in variouscombinations, a complete compensated conductance decade may be achievedranging from `zero to micrornhos in ten micromho steps.

lThe sum of the capacitances of the compensating condensers C1, C2, C3and C4 is symbolically indicated as being a part of the constantcapacitance Cmit being understood that these compensating capacitancestogether with the wiring capacitances are included in this constantcapacitance CR along with any variable capacitance which may beconnected between the terminals A and B for initial balance purposes. Inthe event that any one of the conductance elements is inductive insteadof capacitive the compensating capacitor will :be omitted andcompensation provided by bridging the standard conductance element witha capacitor of suitable size in accordance with well-known principles.

In the past the capacitance standard has been a somewhat simplerproblem. Standard capacitors can be constructed quite easily With verylow impurities. However, in order to secure precise adjustment for aninexpensive bridge standard by employing commercially availablecapacitors, it has been necessary to select capacitors which areslightly less than the nominal value and then pad them out with shuntingcapacitors to bring them to the exact nominal value. This means that onthe average about half of the condensers commercially available have notbeen used for the construction of this type of standard. In accordancewith this invention, however, these oversize capacitors may easily beemployed to construct such a standard. For example, in Fig. 3, thecapacitance standard cs comprises a plurality of standard capacitorsnominally indicated as having the values of 100 micromicrofarads, 200micromicrofarads, 300 micromicrofarads, and 400 micromicrofarads,respectively. Each of these standard capacitors is assumed to beoversize by an amount equal to the capacitance of its associatedcompensating capacitor. As an example, the 100-micromicrofarad standardcapacitor is assumed to be oversize by an amount equal tothe capacitanceC1. In the circuit arrangement shown in Fig. 3, one side of all of thestandard capacitors as well as one side of all of the compensatingcapacitors is connected to the B terminal of the standard, while theterminals 6 of the switch blades 3' are all connected together to the Aterminal of the standard. Switch blades 3 are caused to operate betweenswitch points 4' and 5 connected to the standard capacitors and thecompensating capacitors, respectively. It will be obvious that when anyone of the switch blades 3' is moved between points 4 and 5 the netchange in capacitance will be equal to the difference between thecapacitance of the standard capacitor and that 0f its associatedcompensating capacitor. The standard capacitor in each case may beregarded as having inherently therein an admittance component which isundesired and which is eliminated in effect from the standard circuit byreason of the switching arrangement and the compensating capacitor. Asin the case of the conductance standard, the sum of all of thecompensating capacitors Ci, C2', Ca' and C4 together with the wiringcapacitance is included as part of the constant capacitance Ca,schematically shown in Fig. 3. In alternating current bridge practice,the constant conductance and capacitance Ga and CR, respectively, arereferred to as the residual conductance and capacitance of the standard.As previously stated, this residual conductance and capacitance arebalanced out in the Maxwell type bridge by the balancing impedance Zh inthe C-D arm of the bridge as shown in Fig. 1.

In using the standard shown in Fig. 3, the switch blades3 of theconductance standard and 3' of the capacitance standard may be manuallyswitched in various combinations to suit the conductance and capacitancedesired. For convenience it is desired to have them vary progressivelyin one-unit steps from Zero to ten for each of the decade unitsemployed. One form of switching arrangement suitable for this purpose isshown in Fig. 4.

In Fig. 4 a part of the conductance standard of Fig. 3 is shown with twoof the switch blades 3, their associated terminals 6 and their switchpoints 4 and 5. One of the conductance standard elements, the40-micromho element, with its associated compensating capacitor C4 isalso shown. The various switch blades 3 are shown actuated by suitablepush-rods I3, I4 which are preferably made of insulating material. Thesepush-rods rise on a series of properly cut cams 8, 9, I0 and II whichare in turn mounted to a shaft 'I which may be turned by an index knobI2. As the index knob I2 is turned to the required conductance, the cams8, 9, I0 and II are rotated to actuate their associated push-rods I3 andI4. In Fig. 4 the push-rods and the switch blades associated with cams 9and II) have been deleted. Also in Fig. 4 the position of the switch issuch as to set'the standard for 40 micromhos which corresponds to theschematic arrangement shown in Fig. 3. It will be noted that this isachieved by causing the switch blade 3 to contact switch point 4 whichis caused by push-rod I4 being lifted by a swell on cam I I.

It will be understood that each of the cams have eleven positionscorresponding to the conductance settings Zero to ten, inclusive. Thepositions on the respective cams which contain swells are more fullydisclosed by the following table:

Fig. 5 discloses hcw the conductance decade standard elements togetherwith their associated` compensating capacitors may be connected betweenthe A, B standard terminals with a radial type switch commerciallyavailable. When using such radial type switches, it is preferable thatthe switch be of the non-snorting type, that is, the switch blade 3 doesnot bridge adjacent switch points. Should it bridge these points, it isobvious that certain positions would cause the blade to momentarilyshort-circuit the A and B terminals of the standard thereby greatlyunbalancing the bridge and increasing the difliculty of balancing thebridge. It will be noted that as in Fig- 3, the conductance elements areconnected in series with their compensating capacitors between the A andB terminals of the standard. The switch acts merely to short-circuiteither the conductance element or the compensating capacitor, it beingunderstood that the conductance element contains an undesiredcapacitance component equal to the capacitance of its correspondingcompensating capacitor. As in Fig. 3 all the switch points4 of thevarious switches are connected to the B terminal of the standard whileall the switch points -of the various vswitchesare connected to theA-terminal of the standard. When using this type of switch, instead ofhaving only one No. 4 and one No. 5 switch point for each switch as inFig. 3 and Fig, 4, apluralityof-such points must be provided. All theNo. 4 points of eachswitch must bestrapped together and Yall the No.5points must be strapped together as shown schematically in Fig. 5. Asall of the standard elements Aand the compensating elements as well asthe various switch elements bear-reference characters and numeralscorresponding to those shown in Fig. 3, the operation Yof this switch isobvious from the previous description. -It need only be remembered thatthese four switches are ganged together on a common shaft 'I so thattheir brush rotors 3 all rotate simultaneously under control of a singleknob I2 in a mannersimilar to the four cams in Fig. 4.

A capacitance decade switching arrangement for a capacitance decadestandard is shown in F-ig. 6. The same general typeof switch structureis employed here as is employed for the circuit Iof Fig. 5. As in'Fig.3-one side of each of the standard capacitors .as well as the`compensating capacitors is connected permanently to the B terminal ofthe standard. All of the switch blades 3 are connected permanently tothe A terminal of the standard. For each position of the switch eitherthe standard capacitance or the compensating capacitance is connecteddirectly across the A and B terminals of the standard in just the samemanner las previously -described for Fig. 3. The reference numerals andcharacters employed in this ligure also correspond with thecorresponding parts of Fig. 3. While in the case of the conductancestandard of Fig. 5 it was preferable that a non-shorting type switch beused, either a non-snorting or a shorting type may be used for thecapacitance standard of Fig. 6. Because of the better Contact featuresof the shorting type switch it is preferred.

Two types of switch structures have already been described as sui-tablefor the practice of this invention. Figs. l and 8 disclose still anotherfamiliar type of switch structure which may be employed. In Fig. '7, forexample, a conductance decade standard is shown utilizing a drum typeswitch. As in the previous figures the conductance standards areconnected in series with their respective compensating capacitors andeach of these series connections ispermanently connected between the Aand B terminals of thestandard. As vis well known either the drum mayrotate relative to stationary brushes or the brushesmay be moved withrespect to stationary drums. In Fig. '7 it is intended that the drumstrips I5,-I6, Il and I8, which are developments of strips which may bemounted on an insulating cylinder, are caused to rotate and thereby movepast their contacting brushes 19,20, 2l, 22, 23, 24, 25 and. 26.Brushes-21 and '29 maintain connections between .strips I5 and Il andthe A terminal of the standard while brushes 28 and30 maintainconnection between strips IS and I8 to the B 1terminal ofthe standard.`It will be noted that the brushesA I9 to 2S, inclusive, are offset withrespect .to their associated brushes. For example, brush I9 is offset soas to break connection with strip I5 before brush 2U will make contactwith drum I5. This provides the non-shorting feature previouslymentioned with respect to the other. switches. A

`suitable index strip 3l integrallymounted to` Gil .dex 52.

drum strip I5 carries numerals 0 to 10, inclusive, which correspond tothe various settings of the decadeunits zero to micromhos, inclusive.This index strip l.3Irotates with the drum past a stationary-index 32schematically illustrated in Fig. 7 as-an arrow Except for the differenttype of switch structure, the switching operation is identical withthose previously described for the other type switches and furtherdescription is therefore unnecessary.

InFig. 8, the capacitance decade type of standard is disclosed utilizinga drum type switch similar to the drum type switch previously describedfor the conductance standard of Fig. 7 except that the non-snortingfeature which is unnecessary for the capacitance standard is not shown.As in the case of the previously described capacitancestandard, one sideof each of the standard and compensating capacitors is permanentlyconnected to the'B-terminal of the standard, while each of the'drumstrips 33, 34, 35 and l3G is permanently connected to theA terminal ofthe standard through brushes 45, 45,41 and 48, respectively. v,Each ofthe capacitors whether standard or compensating has connected to itsrfree terminal a brush '.31 rto"44,'inclusive. The switching action ofthis vdrum type switch is identical with the switching-action of theother'types previously described. As in Fig, 7, so also in Fig. 8anindex stripll isintegrally attached to drum strip 33 and carries thenumerals 0 to 10, inclusive. This index strip is caused to move pastastationary index schematically illustrated as an arrow 50.

In all of the previous iigures the invention has been appliedexclusively to the construction of an admittance standard. However, theinvention is equally Vapplicable to an impedance standard whichmaycontain unwanted or undesired impedance components. This is illustratedfor an inductance Ystandard in Fig. 9. When an inductance standard isconstructed for measuring inductance,l it is usually used in a bridge ofthe comparison type in which case the standard would ordinarily beconnected between the A and D corners, vwhile the A-Band B-C arms wouldbeemployed as ratio arms of the bridge. The `unknown as in Fig. l wouldbe between the C and D corners of the bridge. In.Fig..9 the switching isaccomplished by .means of radial type switches of the type previouslyillustrated in Fig.

I5. In /Fig.r9 this type of. switch is shown ina developed form. VAllthe switch blades 3 are V.ganged together and caused to move around theswitch` simultaneously as previously .described for Fig. 45. :These .areactuated manually through a knob (not shown) which carries with it anin- This index 52 moves adjacent to a, stationary scale 5I inscribedfrom 0 to l0, inclusive.

fWhile 'this index strip 5I is shown developed straight in Fig. 9 itWill be understood that for a radial type switch it isnecessary that itbe curved `or arcuate in form.

.an undesired lresistance component. For example, the-inductance elementL1 may be expressed as having the complex form Ri-I-y'wLi. rFor each ofthe inductance elements the switch blade 3 is caused-to eithershort-circuit the standard in- -ductance element or its compensatingresistor. VIfthe inductance element is to be included in standardcircuit.

those skilled in the use of this type of alternat-.

. blade 3 is caused to short-circuit the inductance element leaving inthe circuit the compensating resistor. Referring to Fig. 9 it will beseen that this will take place each time a switch blade 3 engages aswitch point 5, while each time the blade 3 engages a switch point 4,the associated inductance element is switched into the circuit.

As in the previous gures it will be observed that with only fourstandard elements of l-millihenry, 2-rnil1ihenry, 3-millihenry andLlr-millihenry inductance, a complete decade with 1- millihenry stepsfrom to 10 millihenries may be achieved. Also it will be observed thatthe total resistance component of the standard inductance will always beequal to the sum of the four compensating resistors R1, R2, R3 and R4.In this manner whether or not any particular inductance element isswitched in or out of the circuit, the total resistance component of theentire standard is always the same.

It will be obvious that while several different types of specificswitching structures have :been disclosed embodying the invention, thesame principle is used in every case, that is to say, either thestandard element containing the undesired components is switched intothe circuit while its corresponding compensating element is switched outor the standard element is switched out while the compensating elementis switched into the It will be appreciated by all ing current bridgethat this invention greatly increases the speed with which measurementsmay be made. It will also be appreciated that various other speciiictypes 0f switching structures may be employed to accomplish the sameswitching` scheme and therefore may be used to practice this invention.Each of these switching schemes should be regarded as equivalent tothose specically herein disclosed. It may also be pointed out that theswitching circuit disclosed in Fig. 3 for the conductance component gsmay be interchange'd with the circuit disclosed for the capacitancecomponent Cs but the circuits as selected for these two components inFig. 3 are preferred. For low frequencies there would be littleadvantage in either circuit but at higher frequencies there is a realadvantage in selecting them as illustrated schematically in Fig. 3.Should the circuit shown for the capacitance componentin Fig. 3 be usedfor the conductance component, the conductance elements would be openwhen `switched out of the circuit instead of being shortcircuited.Nevertheless, at higher frequencies the stray capacitance between thefree terminal of the conductance element and various switch parts wouldcouple the conductance element into the standard circuit which, withoutextra shielding, would introduce an uncontrollable error rendering thestandard useless for accurate measurements. For this reason theshort-circuiting arrangement for the conductance component gs ispreferred as shown in Fig. 3, using non-shorting type switches aspreviously described.

For the capacitance component Cs a similar objection arises. conductancecomponent be used for the capacitance component and the measurements bemade at higher frequencies the contact resistance of the shortingswitches may become an uncontrollable factor which would again renderthe, standard Should the circuit shown for the l0 useless for accuratemeasurements. Therefore, the switching scheme as shown in Fig. 3 for thecapacitance component is preferred.

Attention is also called to the obvious fact that this invention may beapplied to compensating a standard element for more than the oneundesired component specifically disclosed herein, the additionalcompensating elements being connected in the same manner as the onesillustrated. This, however, is ordinarily unnecessary.

What is claimed is:

1. An adjustable compensated alternating current bridge standard of thedecade type comprising a pair of terminals for said standard, a multipleposition switching means, a plurality of standard circuit elements lessthan ten in number and having undesired circuit components inherenttherein, one compensating element for reach standard element havingcomponents of the same kinds and magnitudes as the undesired inherentcircuit components of its standard element, circuits connecting thestandard elements, the compensating elements and the switching means tothe pair of terminals, said circuits and switching means being adaptedto selectively connect the standard elements in a plurality ofpredetermined and arbitrary combinations between said pair of terminalsand to automatically substitute between said terminals the compensatingelement for each standard element not so connected.`

2. An adjustable compensated alternating current bridge standard of thedecade type comprising a'pair of terminals for said standard, aplurality of standard circuit elements less than ten in number and eachhaving undesired circuit components inherent therein, one compensatingelement for each standard element, said cornpensating element havingcomponents of the same kinds and magnitudes as the undesired inherentcircuit components of its standard element, a multiple-position switchfor each standard circuit element and its associated compensatingelement, circuits connecting the standard elements, the compensatingelements and the switches to the pair of terminals, said circuits foreach switch being adapted to alternately connect either the standardelement or its associated compensating element in circuit between saidpair of terminals, control means for operating all of said switches in apredetermined and arbitrary sequence whereby said standard elements areselectively connected in predetermined and arbitrary combinationsbetween .said pair of terminals and said compensating elements arecaused to replace between said terminals any corresponding standardelement not so connected.

3. An adjustable compensated admittance standard of the decade typecomprising a pair of terminals for said standard, a multiple-positionswitching means, a plurality of standard admittance elements less thanten in number and having undesired admittance components inherventtherein, one compensating admittance element for each standard, saidcompensating element having components of the same kinds and -magnitudesas the undesired inherent compobeing adapted to selectively connect thestandard elements in a plurality of predetermined and arbitrarycombinations between said pair of terminals and to vautomaticallysubstitute between said terminals the compensating element for eachstandard element not so connected.

4. An adjustable compensated admittance standard ofthe decade typecomprising a pair of terminals for said standard, a plurality ofstandard admittance elements less than ten in number and each havingundesired admittance components inherent therein, one compensatingadmittance element for each standard element, said compensating elementhaving components of the same kinds and magnitudes as the undesiredinherent componentsof its standardr elementy a multiple-'position switchfor each standard element and its associated compensating element,circuits connecting the standard elements, the compensating elements andthe switches to the pair of terminals, said circuits for each switchbeing adapted to alternately connect either the standard element or itsassociated compensating element in circuit between said pair ofterminals, control means for operating all of said switches in apredetermined and arbitrary sequence whereby said standard elements areselectively connected in predetermined and arbitrary combinationsbetween said pair of terminals and said compensating elements are causedto replace between said' terminals any corresponding standard elementnot so connected.

An adjustable compensated conductance standard of the decade typecomprising a pair of terminals for said standard, a multiple-positionswitching means, a plurality of standard conductance elements less thanten in number and having undesired admittance components inherenttherein, one compensating element for each standard element havingcomponents of the same kinds and magnitudes as the undesired inherentcomponents of its standard element, circuits connecting the standardconductance elements, the compensating elements and the switching meansto the pair of terminals, said circuits and switching means beingadapted to selectively connect the standard conductance elements in aplurality of predetermined and ar bitrary combinations between said pairof terminals and to automatically substitute between said terminals thecompensating element for each standard conductancev element not soconnected.

6. An adjustable compensatedv conductance standard of the decade typecomprising a pair of terminals for said standard, a plurality ofstandard conductance elements less than ten iny number and each havingundesired admittance components inherent therein, one compensatingelement for each standard element, said compensating element havingcomponents of the same kinds and magnitudes as the undesired inherentcomponents of its standard element, a multiple-position switch for eachstandard element and its associated compensating element, circuitsconnecting the standard elements, the compensating elements and theswitches to the pair of terminals, said circuits for each switch beingadapted to alternately connect either the standard element or itsassociated compensating element in circuit between said pair ofterminals, control means for operating all of said switches in apredetermined and arbitrary sequence, whereby said standardv conductanceelements are selectively connected in predetermined and arbitrarycombinations between said pair of terminals and said compensatingelements are caused to replace between said terminals any correspondingStandard element not so connected. i

'7. An adjustable compensatedY conductance standard oi'theldecade typecomprising' a pair of terminals for said standard, a pluralityof-standard conductance elements less than ten in number and each havingundesired admittance components inherent therein, one compensatingelement for each' standard element, said compensating element havingcomponents of the same kinds and magnitudes as the undesired inherentcomponents oi its standard element, a multipleposition switch for eachstandard element and its associated compensating element, circuitsconnecting each standard element in a series circuit with itscorresponding compensating element, other circuits connectingeach ofsaid series circuits to its corresponding multiple-position switch, saidswitch and said other circuits being such as to alternatelyshort-circuit either the standard conductance element or its associatedcompensating element, a circuit connecting all of said series circuitsin parallel between said pair of terminals, control means forsimultaneously operating all or said switches in a predetermined andarbitrary sequence, whereby said standard elements are selectivelyconnected in predeter mined and arbitrary combinations between said pairof terminals and saidcompensating elements are caused'to replacebetween'said terminals any corresponding standard element not soconnected.

8. An adjustable compensated capacitance standard ofthe decade type:comprising a pair of terminals for said standard; a'multiple-pcsition'switchingl means, a plurality of standard capacitance elements less thanten' in number andhavingundesired admittance components inherenttherein, one compensating element for each standard element havingcomponents of the same kinds and magnitudes'as-'the undesired inherentadmittance' components oi its standard element, circuits connecting` thestandard clements, the compensating elements and the switching means tothe pair of terminals, said circuits and switching means being adaptedto selectively connect the standard elements in a plurality ofpredetermined and arbitrary combinations between said pair of terminalsand to automatically substitute between saidv terminals thecompensatingelement for each standard element not so connected.

9. An adjustable compensated capacitance standard of the decade typecomprising a pair of terminals for said standard, a pluralityv ofstandard capacitance elements less thanY ten innumber and each havingundesired admittance components inherent therein, one compensatingelement for each standard element, said compensating element' havingcomponents of the same kinds and magnitudes as the undesired inherentadmittance componentsfof its standardA element, a multiple-positionswitch for eachk standard capacitance element and its associatedcompensating element, circuits connecting the standard elements, thecompensating elements and the switches to the pair of terminals, saidcircuits for each switch being adapted to alternately connect either thestandard element or its associated compensating element in circuitbetween said pair of terminals, control means for operating all of saidswitches in a predetermined and arbitrary sequence, whereby saidstandard elements are selectively connected in predetermined andarbitrary combinations between said pair of terminals and saidcompensating elements are caused to replace between said terminals anycorresponding standard element not so connected.

10. An adjustable compensated capacitance standard of the decade typecomprising a pair of terminals for said standard, a plurality ofstandard capacitance elements less than ten in number and each havingundesired admittance components inherent therein, one compensatingelement for each standard element, said compensating element havingcomponents of the same kinds and magnitudes as the undesired inherentadmittance components of its standard element, a two-position switch foreach standard element and its associated compensating element, saidtwo-position switch comprising two switch points and a blade, aconnection from each standard capacitance element to one of the switchpoints or" its associated two-position switch, a similar connection fromeach compensating element to the other switch point oi its associatedtwo-position switch, a circuit connecting all of said switch blades toone of the terminals of said pair of terminals, another circuitconnecting all of said standard and compensating elements to the otherterminal of said pair of terminals, said switches and said connectionsto each standard and compensating element being adapted to alternatelyconnect either the standard element or its associated compensatingelement in circuit between said pair of terminals, control means foroperating al1 of said switches in a predetermined and arbitrary sequencewhereby said standard elements are selectively connected inpredetermined and arbitrary combinations between said pair of terminalsand said compensating elements are caused to replace between saidterminals any corresponding standard element not so connected.

11. An adjustable compensated inductance standard of the decade typecomprising a pair of terminals for said standard, a multiple-positionswitching means, a plurality of standard inductance elements less thanten in number and having undesired circuit components inherent therein,one compensating element for each standard element having components ofthe same kinds and magnitudes as the undesired inherent circuitcomponents of its standard element, circuits connecting the standardelements, the compensating elements and the switching means to the pairof terminals, said circuits and switching means being adapted toselectively connect the standard elements in a plurality ofpredetermined and arbitrary combinations between said pair of terminalsand to automatically substitute between said terminals the compensatingelement for each standard element not so connected.

l2. An adjustable compensated inductance standard of the decade typecomprising a pair of terminals for said standard, a plurality ofstandard inductance elements less than ten in number and each havingundesired circuit components inherent therein, one compensating elementfor each standard element, said compensating element having componentsof the same kinds and magnitudes as the undesired inherent circuit.components of its standard element, a two-position switch for eachstandard circuit element andi its associated compensating element,circuits connecting the standard elements, the compensating: elementsand the switches to the pair of termi-- nals, said circuits for eachswitch being'adapted to alternately connect either the standard elementor its associated compensating element in circuit between said pair ofterminals, control means for operating all of said switches in apredetermined and arbitrary sequence whereby said standard elements areselectively connected in predetermined and arbitrary combinationsbctween said pair of terminals and said compensating elements are causedto replace between said terminals any corresponding standard element notso connected.

13. An adjustable compensated inductance standard of the decade typecomprising a pair of terminals for said standard, a plurality ofstandard inductanoe elements less than ten in number and each havingundesired circuit components inherent therein, one compensating elementfor each standard element, said compensating element having componentsof the same kinds and magnitudes as the undesired inherent circuitcomponents of its standard element, a two-position switch for eachstandard element and its associated compensating element, a' circuitconnecting the standard elements and the compensating elements in seriesbetween said pair of terminals, circuits connecting each two-positionswitch to its associated standard inductance and compensating element,said circuits for each switch being adapted to alternately short-circuiteither the standard element or its associated compensating element incircuit between said pair of terminals, control means for operating al1of said switches in a predetermined and arbitrary sequence whereby saidstandard elements are selectively connected in predetermined andarbitrary combinations between said pair of terminals and saidcompensating elements are caused to replace between said terminals anyycorresponding standard element not so connected.

HENRY T. WILHELM.

REFERENCES CITED The following references are of record in the iile ofthis patent:

UNITED STATES PATENTS Hague, Alternating Current Bridge Methods; PitmanPublishing Co., New York, 1938.

